I think it's MAP10: Refuelling Base (Sandy Petersen). Playing it for scratch, you get the best ballance ever. Monsters everywhere, but everywhere for you to hide, because the place is completely circular. And if you end up with the Cyber at the bad time, you're in deep shit, because he's devious. Even with both the BFG and invuln I was having trouble! Great level.

I hardly think I'll ever see a homebuilt level so non-linear like this (except perhaps '94s and '95s and others.)

What, didn't he quit id Software before DOOM 1 was released? or is this converted from an older DOOM 1 series? (MAYBE YEAH, CUZ I REMEMBER-OR NOT-THAT THIS WAS WITHIN A DOOM 1 ALPHA...) Sorry I haven't looked in his site, for time constraits. Thanks anyway.

THE CITADEL--another strangie. Almost all textures are from DOOM 1, as well as many monsters. This could easily be a map converted from DOOM 1 and it looks kinda ugly. But I don't hate it...

Tenements (map17) and The Chasm (map24) have always been two of my top favourite levels. The first has a good sense of place and is nicely interconnected, and the later just has cool athmosphere and is weird in an unsettling way.

Industrial Zone (map15) is also pretty cool because of the scale and the ammount of non-linearity.

Omg.....you can tell i am such a freakin' n00b....map 30...just jkin, ummmmmm map 07 always made me happy, especially the arachnatron bit, i turned off the music and all i got was....bang bang *gurble..dead* over and over and over and over

Underhalls-map 02. It always captivated me how the chainsaw in the first levle would be immediately be put into use into someone's back. I also appreciated the technique, you know. The way you had to get the key to flip the switch to get access to that other part of the level, wait thats in all doom levels.

Uhm... in my opinion, the best levels of "Doom 2" are "Refueling Base" (because of its gloomy atmosphere!) and "O of Destruction" (because of its different architecture!)... I like also "Gotcha!", but just because I've always liked the weird but fun challenge between the CyberDemon and the Spider MasterMind. ;)

Map 28 is awsome. It was always a good challenge from a pistol start because you just can't run by the pain elementals. It is either that or level 7, which was really, really fun. I find it easy to run around the outside ring shooting at the manubuses with the super-shotgun.
I always had fun outrunning the barrels in map23.